Aims: To evaluate the potential risks of dental treatment during pregnancy and effects on childhood development. Procedures and techniques: We are collaborating with the Avon Longitudinal Study of Pregnancy and Children (ALSPAC). They have collected data on the pregnancies of 14,000 women and their children and we are analyzing the data to look at the relationship between dental treatment during pregnancy (exposures to infection and to mercury vapor), prenatal and postnatal fish consumption and childhood development. Accomplishments: We have looked at the relationship between the questionnaire measures and umbilical cord mercury levels. There is a strong correlation between reported fish consumption and umbilical cord mercury levels, which suggests that the umbilical cord measure may be a useful measure of fetal exposure to methyl mercury. Working with Dr. Julie Daniels, who will be taking the lead on some of these analyses, we are in the process of analyzing the relationship between dental treatment during pregnancy, prenatal and postnatal fish consumption on two childhood development scales, the Denver developmental Scale and the Macarthur communication scale. Preliminary results suggest that dental mercury exposures did not have an adverse effect on child development at 18 months as assessed by these two scales. In addition, fish consumption appeared to be highly protective.